diff --git a/addons/mail/models/mail_composer_mixin.py b/addons/mail/models/mail_composer_mixin.py
index a17b5941199..797a6ad3946 100644
--- a/addons/mail/models/mail_composer_mixin.py
+++ b/addons/mail/models/mail_composer_mixin.py
@@ -26,6 +26,8 @@ class MailComposerMixin(models.AbstractModel):
         'Contents', compute='_compute_body', readonly=False, store=True,
         render_engine='qweb', render_options={'post_process': True}, sanitize=False)
     template_id = fields.Many2one('mail.template', 'Mail Template', domain="[('model', '=', render_model)]")
+    # Language: override mail.render.mixin field, copy template value
+    lang = fields.Char(compute='_compute_lang', precompute=True, readonly=False, store=True)
     # Access
     is_mail_template_editor = fields.Boolean('Is Editor', compute='_compute_is_mail_template_editor')
     can_edit_body = fields.Boolean('Can Edit Body', compute='_compute_can_edit_body')
@@ -46,6 +48,16 @@ class MailComposerMixin(models.AbstractModel):
             elif not composer_mixin.body:
                 composer_mixin.body = False
 
+    @api.depends('template_id')
+    def _compute_lang(self):
+        for composer_mixin in self:
+            """ Take value form template when set. When removing the template
+            reset the value to avoid keeping part of template configuration. """
+            if composer_mixin.template_id.lang:
+                composer_mixin.lang = composer_mixin.template_id.lang
+            elif not composer_mixin.template_id:
+                composer_mixin.lang = False
+
     @api.depends_context('uid')
     def _compute_is_mail_template_editor(self):
         is_mail_template_editor = self.env.is_admin() or self.env.user.has_group('mail.group_mail_template_editor')
diff --git a/addons/test_mail/tests/test_mail_composer_mixin.py b/addons/test_mail/tests/test_mail_composer_mixin.py
index 9591646b4a0..4dd79b17f30 100644
--- a/addons/test_mail/tests/test_mail_composer_mixin.py
+++ b/addons/test_mail/tests/test_mail_composer_mixin.py
@@ -47,8 +47,8 @@ class TestMailComposerMixin(TestMailCommon, TestRecipients):
             'source_ids': [(4, source.id)],
         })
         self.assertEqual(composer.body, self.mail_template.body_html)
+        self.assertEqual(composer.lang, self.mail_template.lang)
         self.assertEqual(composer.subject, self.mail_template.subject)
-        self.assertFalse(composer.lang, 'Fixme: lang is not propagated currently')
 
         subject = composer._render_field('subject', source.ids)[source.id]
         self.assertEqual(subject, f'EnglishSubject for {source.name}')
@@ -84,7 +84,6 @@ class TestMailComposerMixin(TestMailCommon, TestRecipients):
         source = self.test_record.with_env(self.env)
         composer = self.env['mail.test.composer.mixin'].create({
             'description': '<p>Description for <t t-esc="object.name"/></p>',
-            'lang': '{{ object.customer_id.lang }}',
             'name': 'Invite',
             'template_id': self.mail_template.id,
             'source_ids': [(4, source.id)],
diff --git a/addons/test_mail/tests/test_performance.py b/addons/test_mail/tests/test_performance.py
index b929055ccbc..7a57ab192a0 100644
--- a/addons/test_mail/tests/test_performance.py
+++ b/addons/test_mail/tests/test_performance.py
@@ -338,7 +338,7 @@ class TestMailAPIPerformance(BaseMailPerformance):
     def test_mail_composer(self):
         test_record, _test_template = self._create_test_records()
         customer_id = self.customer.id
-        with self.assertQueryCount(admin=3, employee=3):
+        with self.assertQueryCount(admin=4, employee=4):
             composer = self.env['mail.compose.message'].with_context({
                 'default_composition_mode': 'comment',
                 'default_model': test_record._name,
@@ -348,7 +348,7 @@ class TestMailAPIPerformance(BaseMailPerformance):
                 'partner_ids': [(4, customer_id)],
             })
 
-        with self.assertQueryCount(admin=35, employee=35):
+        with self.assertQueryCount(admin=34, employee=34):
             composer._action_send_mail()
 
     @users('admin', 'employee')
@@ -358,7 +358,7 @@ class TestMailAPIPerformance(BaseMailPerformance):
         test_record, _test_template = self._create_test_records()
         customer = self.env['res.partner'].browse(self.customer.ids)
         attachments = self.env['ir.attachment'].with_user(self.env.user).create(self.test_attachments_vals)
-        with self.assertQueryCount(admin=3, employee=3):
+        with self.assertQueryCount(admin=4, employee=4):
             composer = self.env['mail.compose.message'].with_context({
                 'default_composition_mode': 'comment',
                 'default_model': test_record._name,
@@ -369,7 +369,7 @@ class TestMailAPIPerformance(BaseMailPerformance):
                 'partner_ids': [(4, customer.id)],
             })
 
-        with self.assertQueryCount(admin=38, employee=38):
+        with self.assertQueryCount(admin=37, employee=37):
             composer._action_send_mail()
 
     @users('admin', 'employee')
@@ -426,7 +426,7 @@ class TestMailAPIPerformance(BaseMailPerformance):
     def test_mail_composer_nodelete(self):
         test_record, _test_template = self._create_test_records()
         customer_id = self.customer.id
-        with self.assertQueryCount(admin=3, employee=3):
+        with self.assertQueryCount(admin=4, employee=4):
             composer = self.env['mail.compose.message'].with_context({
                 'default_composition_mode': 'comment',
                 'default_model': test_record._name,
@@ -437,7 +437,7 @@ class TestMailAPIPerformance(BaseMailPerformance):
                 'partner_ids': [(4, customer_id)],
             })
 
-        with self.assertQueryCount(admin=35, employee=35):
+        with self.assertQueryCount(admin=34, employee=34):
             composer._action_send_mail()
 
     @users('admin', 'employee')